Many computer systems utilize graphical user interfaces (GUI's) to permit user interaction with data stored in such systems. In a GUI environment, users are typically able to interact with a computer system through intuitive operations such as "pointing and clicking" on graphical user interface controls with a pointer controlled by a mouse or other user interface device. Data is often presented to a user in a GUI environment using a graphical user interface component known as a window. In many computer systems, data to be presented in a window is commonly referred to as a "document".
Similar to a physical window that typically offers a view of only a portion of a person's surroundings, a GUI window typically provides a view of only a portion of the data in a document. Consequently, whenever the amount of data in a document is too great for the entire document to be displayed in a window at the same time, many computer systems rely on graphical user interface controls referred to as scroll bars to permit a user to access different portions of a document.
A scroll bar typically permits a user to scroll in a predetermined direction (i.e., vertically or horizontally) through manipulation of various controls on the scroll bar. For example, many scroll bars include an elongated scroll region, or track, that represents the overall size of the document in the direction of the member. A slider is anchored on the track at the relative position of the portion of the document that is displayed in the window. The slider may be a fixed size, or may have a variable size along the length of the track to represent the relative size of the portion of the document displayed in the window. By depressing a mouse button while the pointer is disposed over the slider, and then moving the pointer along the length of the track while the mouse button is depressed, a user is typically permitted to scroll through the document (an operation known as "dragging" the slider).
A scroll bar may also include a pair of arrow buttons (also known as unit increment and decrement controls), disposed at each end of the track that permit line-by-line scrolling through the document in response to pointing and clicking on the buttons. Moreover, some scroll bars additionally permit a user to scroll screen-by-screen or page-by-page (known as a block increment or decrement) by pointing and clicking directly on the track between the slider and one of the arrow buttons.
In many instances, a conventional scroll bar permits access to an entire set of desired data that a user wishes to view, which often requires that the entire set of data be retrieved into a computer's memory so that the information in the data set is readily available for display as the user scrolls through the window contents. However, in other instances, it may not be desirable to retrieve an entire data set at once, but rather, to retrieve such a data set in pieces.
For example, a number of computer systems rely on a "client-server" model for information retrieval. In a client-server system, information is primarily stored on a relatively large and high performance server computer accessible by multiple users. Each user desiring to access the information on a server does so through his or her client computer, e.g., a personal computer or terminal. Users make requests for information via their client computers, which are transmitted to the server computer for processing. The requested information is then returned to the client computers for display. As an example, many database systems are configured as client-server systems, whereby users pass requests to a server to search for and locate individual "records" of data that match a particular search criteria.
In many client-server systems, a caching mechanism is used to improve usability. Specifically, whenever a client requests a relatively large data set, data is transmitted from the server to the client in "subsets", or chunks of data from the overall data set. Thus, for example, if a user's request results in 10,000 records matching the request, the information might be returned to the client in 1000 record increments that a client could separately request one at a time to permit viewing of the entire data set.
Caching a data set often improves performance since transmitting a large data set all at once to a client over a network ties up server and network resources, and increases the response time back to the client. Caching a data set also decreases the requirements on client computers, since such client computers might otherwise require additional memory and or external storage to store a large data set.
In a GUI-based client, subsets of data from a desired data set are often displayed in a window. Moreover, whenever the display area required to display a subset of data exceeds the display area allocated to a window, a scroll bar is provided to permit a user to scroll within the subset. Selection of different subsets of data, however, is handled through a separate user interface mechanism--typically a series of data set controls such as buttons that a user can select to retrieve the previous or next subsets in a desired data set (e.g., "show previous 1000 records", or "show next 1000 records). Controls may also be provided to permit a user to go directly to first or last subsets. Typically, the subset size is fixed, or at the most, buried in configuration settings that are not readily accessible by the user.
A number of drawbacks exist with respect to conventional mechanisms for accessing subsets of data from a data set. First, a user often has little or no flexibility in varying the size and/or specific range of data to view from a data set. Thus, for example, a user is often not permitted to specify retrieval of just records 1725 to 1775 of 10,000 with a conventional user interface mechanism. Moreover, a user often is presented with little feedback that allows the user to determine where in the overall data set the current subset of data fits, or to determine what percentage of the overall data set is currently being accessed through the window.
Of particular concern is that, without the ability to readily configure the size of a subset, a user is limited to the size dictated by the server, which may limit the user's flexibility. For example, if a 1000 record subset size results in subsets being returned that exceed the storage capacity of a client, that client may not be able to store an entire subset, or may perform slowly. Also, if the amount of data in a particular subset is relatively large, the amount of information displayed in a window may be relatively great, requiring the user to scroll extensively through the window to locate specific information. Performance of the scroll bar for the window in such an instance may also be degraded because the scroll bar may become too sensitive and make it difficult for a user to scroll to a precise location in the window.
Therefore, a significant need exists in the art for an improved manner of improving access to information in a graphical user interface environment, particularly in client-server computer systems and the like.